Glow plug for internal combustion engines



I www Filed Aug. 1, 1939 ,Orn/rf?,

April 30, 1940.

"Patented'Apn 30,` 1940 UNITED STATES GLowrLUe Fon ENGINES Eli White, Detroit, Mich., assigndfof one-tenth.

to Otto Milbrand, Detroit, Mich.

Application August 1, 19139, SerialNm 287,809 reclaim. (01. 12a- 145) I This invention relates to` glow plugs for use in the ignition of a combustible mixtureor foruse in ignition of the fuel charges of internal combustion engines particularly of the fuel injection ,it type commonly referred `to as `Diesel; engines.

The object of the invention is to provide a new and improved means for igniting a combustible mixture by a heated element, the initial heat of which is produced by anelectric current and including means for `automatically breaking the circuit subsequent to an initial heating period. More specifically an `object and feature of the invention is to provide atmeans for initially heating theplug priorto operationv of the engine by a manually closable circuit ofla comparatively high` amperage so that the plug may be brought to a glowing condition for ignition of the fuel charge in operation of `the engine. I

In the form of plug shownAi-n my` previous application for` patent for Glow plugs, Serial No. 234,639, the means for maintaining the` conductor in contact with the portion oftheplug utilized for ignition purposes when the parts are cold, ineluded an internal spring element and therefore "25 in aposition` to become ineiective due to1 detereoration by heat. In the improved structure herein disclosed the spring element is positioned externally of4 the plug and-subject to the cooling" `effect of atmosphere. `Thus `the arrangement is oflonger life period than is the structure shown in said former application. p

A further structuraldifference involved in the device hereinafter `more fully disclosed resides in the fact that.thelspringmaintains the contact `elements of the plug innormally slightly `spaced relation providing a break in an otherwise closed electric circuit, means (preferably electrical) being provided to close the contact elements to initially heat theplug and to insure its attaining ,40 theproper temperature forignition of the fuel charge and to thereafter break the circuit as; the

burning `fuel charge maintains the glow portion of the plug heatedand the `circuit broken.

A further object ofthe inventionis to provide a .glow plug` having a metallicportion subject `to expansion and elongation under heatand a cylindrical shield thereabout formed of a material such an unglazed porcelain `or graphite providing a poor conductor of heat but capable of absorbing In and storing `the heat energy radiated from the metallic plug to therebygdevelop a higher temperature more particularly on the inner surface of the shield than is developed on thesuriace of `the heated glow plug.

. shown.

During the combustion of gases These and other objects and" novel features ofA the invention are hereinaftermore fully described N and claimed andthe preferred form of construction of a glow plugembodying my invention is Y shown in the accompanying drawing in which- Fig. 1 is a vertical section showing my improved glow `plug and circuit` for the initial heating thereof.

Fig. 2 is a vertical section of an alternative form of the device. l

In the form of invention shown in Fig. 1 the glow plug comprises a metallic body I the exterior surface of which may have a hexagonal form in crosssection adaptingit for use by a wrench to screw the threaded end 2 into the threaded aperture at the head of the engine cylinder indicated by dotted lines 58 or other apparatus, not here This body I has a hollow interior 3 formed with a shoulder 4 at the upper end thereof to receive the shank or base 5 externally of the glow plug Vwhich is shouldered to seat on the shoulder 4. This base 5 and the` internal recess l is preferably cylindrical i-n form and the lower end 6 of the plug is of less diameter than the base portion 5 and is connected therewith by a tapered cone like wall L` At the junction of the portions 6. and 'I, the tube is threaded at 8 and a porcelain or like cylindrical shieldvSjfis threaded thereunto. The body oftheshield is` spaced from the portion `I5 of the glow plug and is providedwith apertures I6 adjacent the threadedend thereof permitting free flow of gases in the combustion chamber `of the `engine intoI the shield and about the plug end` 6, the shield being open at the lower end II. in the cylinder,

the portion 6 of the tube is maintained at ignition temperaturey and the shield 3 being a poor coni ductor of heat, such as unglazed porcelain or graphite, becomes highly heated by the radiant 'energy from', the glo-w plug. By such means, when the glow plug is heated to practically incandescence, radiant energy is transferred outwardly from theplug and heats the shield. Subsequent to the heating of the `glow plug by the electric current and starting the operation of the engine the heated gases in combustion maintain the shield and plug practically incandescent.

The body I is of metallic character and has a centrally apertured cap I2 formed of an insulating material. The upper end of the conductor I3 is threaded and a nut I4 is threaded thereon and a second nut I5 is also threaded thereon and between the two there is a shouldered spacing ring` I6 preferably of insulating material. A U shaped spring I'I has an` out-turned base portion I8 .for attachment to thebody I as by a screw I9 and the A other arm 20 of the spring is apertured to engage over the reduced diameter portion of the shouldered spacing ring I6. A screw 2I is inserted through an aperture in the arm and is threaded in the arm I1 of the spring and, by turning the screw in or outof the threaded aperture, the Spacing between the contact elements I3 and I3 may be varied. The contact element I3' has its lower end ZZfiXed in the terminal end` 6 of the glow tube. Due to the glow tube 6 being formed of metallic alloy, as for instance a chromium" alloy, it will become highly heated due to its resistance to ow of electric current through fthe conductors I3 and I3' when in contact, as will be hereinafter described.4 The spring 20 normallyr spaces the nut I4 from the insulating memof current supply 24 and connected with the metallic body I within which the upper end of the glow tube is in electrical contact and thus current passes through the glow tube, the conductor ele- `ments I3 and I3 and through the fastening greater surface area thereof in contact gases and due to the higher temperature thereof screw 25 and thence through line 26 to the battery,.it being understood that the circuit is normally open by reason of the spacing of the elements I3 and I3.

The second circuit indicated at B consists of the wire 21 connected to the battery 24 when the switch 28 is closed and this wire 21 leads to an electro-magnet 29 and thence by a line 30 and line 26 to the opposite side ofthe battery. Thus by closing the switch 28 the electro-magnet tends to draw` the arm 20 of the spring toward the magnet and placing the members I3 and I3 in contact and closing the circuit A thereby heating the tube 6. As this tube elongates longitudinally due to heating the spring arm 20 will continue to move toward the magnet until the nut I4 engages the upper surface of the insulating cap I2 for the casing I. This arrangement is providedv to prevent the breaking of the circuit prior to the tube S attaining incandescence and by adjustment of the nuts I4 and I5 the gap between the member YI4 and the cap I2 may be varied to provide for a greater or less period of time of electrical contact between the two partsl I3 and I3.

By holding` the switch 2B closed, current will pass through the conductors and the tube portions 5 and Ii but, as the tube ends 6 become suffi- .ciently elongated by heating, the circuit through the conductor elements I3 and I3' will be automatically `broken and the tube 6 maintained in practicallyv incandescent condition by the heat developed by the combustion of gases.`

The apparatus will function efficiently without the shield 9 but by use of the shield 9, of a refractory material and a poor conductor of heat, it

becomes highly heated and the efficiency of the glow plug is increased Vsomewhat dueto the with the and to the fact thatgases may pass into the interior of the shield aswell as to Acontact with the exterior thereoixlt is for this latter purpose that the apertures lIll are provided whichpermit iiow of gases therethrough during the compression stroke of the. engineand thus the chamber between the glow plug 6` and inner wall of the member 9 does not become iilled with burned gases.

While I have described the parts I3 and I3 being normally slightly spaced apart, as shown, the apparatus will function if these two parts of the conductor are normally in contact and thus -ing the inward movement of the member I3 and thus providing that further expansion of the tube 6 will cause separation of the member I 3' from the companion element I3.

While'I-have described the use of an electromagnet and circuit therefor as a means of moving the' arm 2B to force the contact element I3 downwardly in Athe position of the parts here shown to contact with the conductor element I3 other means for such purpose may be utilized Without departing from the spirit and scope of this invention as defined by the appended claims. The electric circuit for the initial heating of the glow plug is an essential characteristic and considered' the most desirable means for the initial heating of the plug.` y

In the form of the'invention shown in Fig. 2 the body 40 is practically identical in form to the body I of Fig. 1 and thevupper end of the glow tube 4I is shouldered to seat in the upper end of the body 40 which has a cap 42 of insulating material. Within this body is a conductor formed of two parts 43 and'44secured together or made of an integral piece with the end portion 44 of less diameter than the portion `43.`

To maintain theconductor withfthe end of thev portion 44 in contact with the enlarged end 45 of the glow tube, und'er normal condition, I provide i aU spring 48having one leg attached to the body portion by the screw 49 and the two arms of the spring are held in adjustedv position by the screw A5I! which passes through an aperture in the upper armv of thespring and rinto a threaded aperture in the lower arm of the spring. The upper arm of the 'spring engages a shouldered element 5I positicned between the two adjusting nuts 52 and' 53 threaded on the upper threaded end of the conductor body 43. The springis tensioned to normally. provide pressure'between the end 44 of the conductor'and the surface 41 of the glow tube 43 and with the nut 53 normally spacedv from the cap 42 and the spacing maybe variedby threading the nuts 52 and 53 inwardly or'outwardly on the conductor body 43. There is an electric circuit 54 having a source of current supply, as a battery 55, and a switch element 56 therein utilized to make or break the circuit. Said circuit has one end connected with the body 4I! and the other end connected with a screw 51 at the end of .the conductor body. By vclosing the switch 56 current passes from the battery to thebody 4B into the glow tube and thence through the conductors 44 and 43 back to the battery.

` iorniedlofmhroinium alloy or iotheifelec'trically `tenueto elongate. f Due to 1 the sp1-lingua `beim;

` i electric contact, said" contact* willj be maintained the period "required for the nut 53 `t`o`` move "'to contactlwith the face "of the' insulatormem- I ber 42. Continued heating of] the tube^46 and fio .1 consequentV further l elongation thereof will 11move .the edited face trof the @11u45 of the tube' out ofgfcor'itafctA witlitheconductor element 44.` Thus, i

` on@ the assumption" thatxthe switch E remains 'closed (which is the `normal condition in initially H5 "heating the` glow tube)l the circuit will be broken separation ofthe elements 44 and 45 andthe tube willbe Vmaintainedin heated condition ,due

t" the heat df the gases in combustion and "con- `ue `to "automatically `ignite the fuel when inl contact therewithpwhether the glow 1tube bei used in aninternal combustion "engine otherapparatus fsulpplied "l with combustible fuel flatfintervals; i i i, i i i lBy usef'of themass of` metal Y45 4at the end of he' glow tube 46 landbreaking the circuitatthe 3 lendloithe' glow tuberather than within the body f thelapparatus', `asshown in 1, lessheatis eloped, witninjthebodyof the plug. i The apfp iatusofFig. 2 further differs from thatshown AKP3Min Figli in that inFig 1 the `spring is electrically l f vactu te'd to nieveV the part I 3` downwardly to pro- "duce initial contact with the conductor elem nt 13'. i li But in eithercase, on the initial heating ofthe "plug bymeans of an electric circuit,` the circuit "is maintained closed forapredetermincd period 'limitedby the spacingof the nuts I4 or 53`relaf tive to the cap` l2 `or 42 in the respectiveforrns.

`Both structures function alike in the initiallieating ofthe plug in which therespective conductors Wareiormed of metal of low electrical `resistance l i andthe glow tube is a metal of high electrical re-` sistance elongating under innuence of temperature and thus functions tof break an established electrical circuitthrough the conductor after af predetermined `period of heating.

` From"theforegoing.description it is believed fjevident that the various features and objectsof the, invention are attained by the construction l5() described and that the parts may be varied in` structure and form without departing from the spirit of the invention as set forthinthe appended claims. i

`Having thus fully describedmy invention, its 55 utility and mode of operation, what I claim and desire to secure by Letters Patent of the United Statesisn l. In a glow plug for ignition. ofacorn'bustible mixture, atube formedlof a metal of .high eleci trical resistance, a conductor centrally disposed within the tube having an end fixed to the end of the p tube, a seco-nd` conductor in longitudinal alignment with the iirst conductor, a spring f normally supporting the second conductor with an end in spaced relation with the end of the first `conductor opposite the Xed end,` an electrical circuit, the saidconductors and tube forminga part of the circuit,` `and means for moving the second conductor td contact `with the first `conductor toclose `the circuit through the `said conductors and tube.

. 2. In a* glow plug for ignition of `a combustible f mixture, an element formed of a metal having a high electrical resistance, a hollow body, said 'f5 electrically resistant elementprojecting from thej sistan'tlelementwhereby it becomesheatedv charges.

12,198,850 l i i -3 Iheglbwffi tube, 1ip'articularly the"l portion'lG'is body Atofeinose the surface :thereoftot"thecom.-v

bustible mixture," a l `two-.part conductor within the `body,'jthe partsV being in longitudinal alignment 1 and one of the conductor parts having an hend"-"securedj to the Vhigh resistant elementwhere- \5 '.by, through the` elongation-of` the'elements" due tto heat, ltlie1"s'ai`cl `icon'clucto-r `part 'attached thereto for moving the second conductor tol contact with thers't conductor to close the circuitthrough `15 the said conductors and element of high. electrical resistance; and means `limiting the" extent of moye'rnen'tof theseco-ndconductor part by said Lin`a11iia`, lly controlled means." Y i 1 f3. Ina/glow plug forignitio-n of a combustible *20 f mixture inthe combustion chamber offanlinl terna-l combustion engine, a` casing having a `threaded end portion for assemblyfin an.4 engine cylinder, having a threadedwaperture therefor, a u

l tubular electrically resistant element having one .25 end secured to the casing, and the opposite end projecting into the end of the cylinder for con]- j tact with the combustible mixture therein, a twopart conductor;` one of the saidfpartsfprojecting from the'casing andmovable longitudinally witli- *330 in the tube,` the other of said parts having an inner end `attached to the `inner endjof vthe `tubular "element and the oppositeend in normally spaced 'relationl with the innerend of the rst conductor part, y,a "Spring externally; of the casing, and 35 j for ,adjusting "the spring `to "h old .the said conductor parts inl normally )spaced relation; an

electric ,circuit includingthe said normally `spaced n conductor parts, and nieans for moving the spring andthe conductor `parts attached there-to `to 40.

bring thesaid two conductor parts in contactto closejthe electric circuit, and means limitingthe movement of thellfrstconductor partwhereby as the electrical *resistance "element is elongated L under heat it is moved from contactfwith the said 45.

`movable conductor element to automatically break .the circuit.

f 4.1Infa glow `plugfor ignition of ai` combustible @mixture in the combustion chamber` of an internal combustion engine having fa threaded'* 60 aperture open to the chamber, a hollow bodyhaving athreaded open end for threading in thesaid l aperture,` .a hollow electrically resistant element Q havingan open end secured within the saidbody f and a sm'ali` .diameter closed` end` projectingf `ISIS j therefromQa pair-oi'` electrically conductive ele- "inentsfthe first `of fthe said elements projecting l" throug`h`1the openifend, of the: body casing, and

` the other being.longitudinallyaligned therewith with anend thereof in normally"spaced` relation* 60 lwith the contiguous fendinfthe ,rst` elementthe innerfend of the second element being secured to the projecting end of the tube, `means .yieidably l. supporting the-conductor partsl in` spaced rela- 65 htion, an electric circuit including thesaid tube and conductor parts normally open byreason of the spacing of thej conductor parts, and means under manual control for moving the `said movable conductor part to close the .circuit throught 70 1 the tubeand the conductor parts, and means for adjusting the extent oflmovernent of the movable conductor element whereby as the tubular element of electrical `resistant metal `elongates under heat the saidconductor` element attached` to'thetubelfis :moved from contact-withthje other conductor felementzand `breaks the circuit.

5.. :In a Lglow `plug' for r-igniting a combustible mixture, Ta 'metal body,y a tube-'carried thereby formed -of af metal rof Ihigh .electrical resistance vand closed at theend in' contact with `thejcom- "bustible mixture, 'a centrally disposed electrical conductor Awithin the tube Jand contacting the '.same'only at Athe closed'fend, a secondfconductor ',providing a .contact member, a spring adjustable4 to normallyprovideganair gap betweenthe conductor element :and the lcontact member, an elec- 'tric circuit normallyclosedexcept for the said yair gap, and 'anauxiliary -circuit including an y electro-magnet functioning Whenithe circuit is closed to move ,the conductor -to close the air gap 4'to ythereby `establish, an electric circuit through the tubecontact member Vand conductor to therey by heat the tube and Aconsequently expand the `same longitudinally, vand means limiting the 4movement of the contact member by the `spring thereof, van electric to less than lthe length y*of the air '.gap produced. bly-elongation'of lthe tube underinfluence of -the `heat of combustion. :25

mixture,a metal body, a -tube carried thereby formed of a =metal 'of high electrical .resistance r6. In .la glow -p-lug -for ignitingr a .combustible vand closed .at the'end linwcontact with the corn- -bustible mixture-a centrallydisposed electrical conductor .within Ithe tube vand contacting the same only at the,closed/end,.a second 'conductor providing va contact member, aspring adjustable 4to normally provideV tan air-gap between the con- -ductor element and the vcontact member, said 'spring `being -mounted 4on. the body externally circuit `normally vcloseclexcept i for `the said air gap, and an vauxiliary circuit vincluding an electro-magnet functioning when the circuit is .closed tov move the conductor to -closetheair gap to thereby establish an-electric circuit through the tube, contact member `and conductor to thereby heat the ltube yand consequently expand 4,the samelongitudinally, and means limiting movement of the contact member by the spring to less than the length oi the `air'gap produced by elongation ofthe tube under iniiuence of the heat of combustion.

.-7. :In .a ,glow plug `for igniting ,a 4combustible mixture, a `metal body, .a ,tube ,carried Vthereby ,formed-of almetal of vhigh electrical `resistance vand-closed yatthe end in :contact with ,the corn-V lbustible .mixture, 7a centrally `disposed electrical conductor within .the tube and -contacting .the vsame fonly at `the A.closedend, asecond .conductor providing a contact vmembenaspring.of U form having one fend I,attached Y,to .the body .and the other rendengaging the second conductor, means for adjusting the.last named end of .the spring .to .normally ,provide ian` air gap between the conductor element and the contact member, an electric circuit normally closedexcept for the Asaid Vairgap, and an auxiliary circuit vincluding an electro-magnet functioning when the auxiliary circuit is closed to move the conductor to close the air gap-to thereby establish an electric circuit :through the tube, contact member and conductor to thereby heat the tube and consequently expand thesame longitudinally, and means limiting thegmovementof the contact member by the spring to less than the length of the air gap produced by 'elongation of 'the f tube under influence of the heat of combustion.

`8. In `a glow .plugffor ligniting a combustible mixture, a :body,-an` electric circuit, an electrical conductor carried-,bythe -bodyand' forming part the plug being `a metal of high electricalresist- `-of the electric circuit; said :conductor fbeing formedbf tlwopartsgone of low electrical .resist--l ance and the 4other of high :electrical aresistance,

said conductor parts being normally spaced, means Yunder manual control for movingthe-low t',

resistancejpart tozcontact with the other to:close .the circuit tothereby heat the part of rhigh electrical resistance and cause an elongation thereof, means limiting the movement of saidlow resistance part lto a `distance :less than move-1U vment .of the said vhigh resistance part by-elongation whereby said conductor parts are `sfeparai'ied andthe circuit automatically broken.

`9'. kIn a glow plug for the ignition :of a com-y bustible mixturea hollowbodyanelectrical con- 15 ductor carried by the .body formed vof two separable ,partsone of low electrical resistance movable relative to the other, andthe other being of va high velectrical resistance, said ,parts vbeing in a normallyspace-:lrelation, :an electric circuitglo including the said conductor parts, `a second electric circuit including anelectro-magnet `functioning when the second circuit is closedtomove the said-movable part of Atheconductor to contact with the high resistance part to therebyn A.close the. rst circuit through the vconductor rpartsfand cause anexpansion ofthe high resistvance element by' current flow therethrough,

means adjustable to Alimit the fextent `of move- .ment of the lower Aresistance part whereby as ,30

the `high resistancepart elongates .by expansion under .heat the .rlrst -saidcircuit is automaticallv broken. l y' f vl0. `A :device .for Ithe ,ignitionof abcmbustible i Imixture-in .an `internal `combustion engine havinge acombustion chamber., .comprising a `hollowbody "having .a threaded .end engaging in a threaded .aperture providedfin .the wall of the .combustion chamber kkofthe engine, aglowplugcarried by the body-and projecting .therefrom into thecOmbuS-o tio-n .chamber for contact with the `.ca'lmbustible gases intermittently supplied thereto, a hollow shield of refractory material .of vlcwheat conduc- -tion .supported at `one vend onfthe `body lof .the

`'glow 4plugfahd in which-theglcW-plug is .centrallym disposed, the opposite end olf .theshieldbeing openy f, andthe Wall .thereof -adjacent .the attached .end v having apertures .providing for flow of combustiblegases through the shield and about the plug, ance .and vforming :part .of Vthe electric circuit,1 5f means whereby the expansion `ofthe ,plug breaks the electric' circuit, the continuedheating .of the plug vby .burning of .the vcombustible 4mixture maintaining thesame in expandedcondition.V 1 5, Tll. A device `forthe ignition of .a combustible" mixture in an internal combustion engine, comprising a body, a glow 4plug'extending therefrom at one end, said body being ,a metal of low electrical resistance and the 4plug being vcfa metal ,6, of a high Aelectrical resistance, a Vvshield having one end thereof secured to theplug at V.a-distance from theend of the plug, and the oppositeend of the shield being open, said shield having apertures .means whereby the expansion of the plug Vbreaks the electriccircuit and continued-heating thereof by the combustiblemixture maintains the plug in expanded condition. 1

12. In an Vignition device for internal combustion engines, an element of high electrical resistance projecting into the combustion chamber of the engine and adapted to be heated by the gases in combustion therein, an electric circuit for an initial heating element, a hollow shield of a refractory material having one end attached to the said element, the opposite open end Qi the shield being adjacent the end of the element, said shield being of a character to become highly heated by the heatingof the plug and combustion of gases in contact therewith, an electric circuit for initially heating` the element, and

`means actuated by the heating and consequent expansion of the element to break the electrical circuit, the said shield and element being maintained at `high temperature b-y the gases in combustion.

13. A device for ignition of a combustible mixture comprising a hollow body, a glow plug carriedthereby 'and projecting therefrom into the combustible mixture, a hollow shield of a refractory material of low heat conduction into which the plug extends, the glow end of the plug being spaced from the inner surface of the shield, and an electric circuit for initially heating the plug to` ignite the combustible mixture, the plug being of a metal of a high electrical resistance and forrning part of the electric circuit,and means whereby the expansion of the plug breaks the electric circuit and the continued heating thereof` by the burning of the combustible mixture maintaining the same in expanded condition.

ELI WHITE. 

